Problem with styled QPushButton clickable area

[koan]

I have styled my QPushButton using the following style. Inside the border of the button and in the corners there are large areas that are not clickable (about 4 pixels inside the button outline). Using :hover I can see that Qt thinks the mouse is over the button but when I click, the button is not drawn as pressed and there is no clicked signal. It's only when the mouse is close to the centre of the button that I can register a click.

I have tried experimenting with padding and margins but this hasn't helped. If I remove enough styling so that the widget looks drawn in the native style then the whole button is clickable.

QPushButton {
  color: #000000;
  background-color: #ffff00;
}
QPushButton:pressed {
  background-color: #4444cc;
}
QPushButton:hover {
  color: #cccccc;
}

QPushButton {
  color: #000000;
  background-color: #ffff00;
}
QPushButton:pressed {
  background-color: #4444cc;
}
QPushButton:hover {
  color: #cccccc;
}

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